Ear protector with adjustable anchoring means



July 12, 1949. M. c. ROSENBLATT 2,476,224

EAR PROTECTOR WITH ADJUSTABLE ANCHORING MEANS Filed Sept. 12, 1944 2 Sheets-Sheet 1 IN V EN TOR.

=JV/aur/ce C, @mmUm A TTORNEv July 12, 1949. M. c. ROSENBLATT 2,475,224

EAR PROTECTOR WITH ADJUSTABLE ANCHORING MEANS Filed Sept. 12, 1944 I 2 Sheets-Sheet 2 INVENTOR.

"- 34 ATTORA/Ey Patented July 12, 1949 UNITED STATES PATENT OFFICE EAR PROTECTOR WITH ADJUSTABLE AN CHORING MEANS Maurice C. Rosenblatt, New York, N. Y.

Application September 12, 1944, Serial No. 553,768

12 Claims. 1

This invention relates to acoustic devices for protecting the ears from loud noises, and is an improvement on the acoustic guard shown in my co-pending application, Serial No. 478,464, filed March 8, 1943, now Patent No. 2,361,963, issued November 7, 1944.

The guard disclosed in said co-pending application embodies the same basic principles as the present device, but an improved, adjustable earengaging means has been devised which forms the subject matter of the present invention. A further improvement has resulted from the fact that it has been found possible to increase the responsiveness of the diaphragm, making it more effective for the intended purpose.

The special use of the invention is to provide a means for protecting the ears of persons exposed to loud noises, particularly military personnel, and also workers in noisy industries, where the constant din has a fatiguing and nerveracking effect, if it does not injure the hearing and ears or produce shell-shock.

The adjustable ear engaging means may be used with other types of instruments which are supported adjacent the ear, as telephone and radio receivers, especially aboard ships and in the Signal Corps, and head phones of all kinds, for supporting the ear-engaging parts of hearing aids, with a combined diaphragm according to this invention and ear phone in hydrophones to protect the listener from heavy shocks caused by explosions in the water close to the transmitter, or as ear plugs for sleepers in areas subjected to bombing without the irritation caused by insertion of a foreign object in the ear canal.

It is an object of the invention to provide an adjustable ear fitting for an acoustic device which provides a firm support for the device without the use of individually molded fittings or external fastening means.

It is a further object of the invention to provide an ear guard which allows ordinary conversations and sounds to be heard clearly, but which becomes progressively more impervious to sounds above a level of 85 decibels.

It is a further object of the invention to provide an acoustic guard having an improved diaphragm of great selectivity and effectiveness.

Further objects of the invention will be apparent from a consideration of the following description taken in connection with the accompanying drawing, in which Figure 1 is a plan view of the inner face of the device.

Figure 2 is a side view of the device shown in Figure 1.

Figure 3 is an end view of the device shown in Figure 1.

Figure 4 is a sectional view of the device on the line 4-4 of Figure 1.

Figure 5 is a sectional view on the line 5-5 of Figure 1.

Figure 6 is a side view of an acoustic guard having a modified form of ear fitting.

Figure 7 is a plan view of the improved diaphragm.

As shown in Figures 1 to 5, inclusive, the improved acoustic guard comprises a casing ID in which is mounted a diaphragm II. The casing I0 is provided with an aperture [2 on its front or outward side 13, and a second aperture 14 on the opposite side l5 of the case. At the opposite or back side I5 of the casing in is secured the means by which the guard is supported in the wearers ear. 7

The support or car fitting is made up of two relatively movable parts, one being a rigidly mounted center piece l6 having a passage ll extending from the outer end and through the neck 19 and base 20. A removable tip [8 of neoprene or soft rubber is mounted on the neck 19. The base 20 is rigidly secured to the back l5 of the casing within the opening [4.

In opposing relation to the rigidly mounted center piece 16 is a movable anchor 21 comprising a crescent shaped projection 22 mounted on a slide 23 which is movable in track forming members 24 secured to the back [5 of the casing. lhe slide 23 and track forming members 24 are beveled as shown at 25, so that the slide is retained on the base. An elongated slot 26 is provided centrally of the slide 23 and the base 20 of the center piece [6 extends through the slot and is permanently secured to the casing 19. The base 20 is cut away at the level of the slide so that it projects over the face of the slide at the edges of the slot.

Within the slot 26 is an expansion spring 21, one end of which is mounted on a projection 28 at the end of the slot 26 adjacent the projection 22. The other end of the spring 21 is received in a socket 29 in the fixed base 20, and the spring, therefore, tends to separate the tip and anchor members.

In assembling the device, the slide 23 is entered in the track formed by the members 24 before the fixed base 20 is secured in the opening Id of the back of the case. The fixed base 20 prevents accidental separation of the slide and case, but the elongated slot 26 in the slide through which the center piece I6 extends, permits the necessary expanding and contracting motion of the parts. of the ear fitting. In use, the anchor 2| is pressed toward'the center piece,. andthe tip is is then inserted at the entrance to the ear canal. The device is held within the shell of they ear while the anchor is allowed to move out wardly until it is engaged in th'euconchaiofthe.

case terminates in a projecting stem 32 at the lower side of the-anchor. Over the stem. 32 is mounted a removable flexible ear tip 33 having a passage lid-extending thereth'rough; Thepart of the tip 33 which is mounted over the stem 32 is provided with a plurality of circular segments 35, and the tip can be shortened easily by-removing the tip and severing the-stem-en aging section at the desired corrugation: This enablestheuser to'adjust the distance between the tip and the anchor to suit his ear.

it is less expensive and more-easilym'ade, and

has its field of usefulness for these practicali reasons;

The improved diaphragm H shown in Figure-'7 I comprises a resilient'disksecured between' the two-sectionsl3 and-lfiof the casing 10'.- Around the. openings 12 and I4 in-the'ca-sing the-interior-of the casing is shaped to provideseats 40 and.

When sound waves of more than ordinary intensity reach the diaphragm; it vibrates-rapidly between the seats, efiectually muiiiing the sound. According tothis invention the diaphragm is provided'with an'aperture 42"near the-rim; and

with a slit 43 extending concentrically around the diaphragm at thesame distance from thecenter as the aperture. The endsyof the slit extendto points adjacent'the aperture, leaving the center 2-4 of the-diaphragm connected to the'rim by a bridge or hinge 45.

diaphragm to sounds of low-freq'uencies. or ordinary loudness pass throu-ghthe apertureor through the-slit, and reach the'wearers earthrough thechannel in the fixedly mountedcenter piece It. The circular slit enhances the responsiveness of the-diaphragm and insures'sufficient freedom of movement in response to loud sound to restrict the openings effectively and reduce the intensity of the sound.

The motion of the diaphragm is'to'some extent that of 'acvibrating reed, as in aamusical instrument. If the gapbetween th'e diaphragm and the ports at thexcenter*ofathedevice-is reduced- While this form-is not as perfectly adapted 'for' adjustmellt to the individual ear as that shown in-Figures1ato 5,

The diaphragm 'l l lies midway between these "seats, except when'subjected to loud noise.

Opposite the bridge 45 the slitis widened at 46 through about 120 of its extent. This increases the responsiveness of the Soundsa position will be reached where the device will actually begin to whistle when exposed to sound. In this condition the diaphragm acts like a reed and augments its own natural responsiveness. This happens because the sound enters the external port and spreading fan wise in the expanding cavity of the case is in turn reflected back to the center of the device. As this sound passes across the face of the diaphragm at the annular slit around the free center of the diaphragm it sets up sound eddies and causes the diaphragm to flutter as a reed does. In other words, a form of resonanceis introduced. Since the device shouldnot whistle, the gap between the face of the diaphragm and the ports is increased just enough so that Whistling is eliminated. The reed action of the diaphragm is retained in reduced amount. and .the response of the diaphragm is augmented to restrict the ports to a greater extent than otherwise would obtain.

It is of particular importance that the device should notice .tOO'lSXIIfi-ll. Former inventors and students of acoustics have had the erroneous impression that they could. improve upon natures work and that they could make a mechanism as sensitive as the eardrum and its auditory chain and linkage- The wishto make sound deadening devices as small=as possib-le'has defeated the purposeybecause, to get any effective acoustical results, thearea andscope of the device must be commensurate with the'length of sound Waves and Fth'eirpowe -"to actuate a mechanism without the introduction-of 'power from an extraneous source; For'example, it is impossible-to make a mechani'oaldevice which-will record accurately a sound waveon paper; The resistance of a minute=drop off'ink betweena stylus that does not actuallytouch'the-paper and the paperitself is sufiicient to prevent accurate movement of the stylus, even when the mechanismis subjected to the *-loudest sound;

There-is a definite relation between the area of an effectivediaphragm and sound vibrations. For examplaasound of 100 vibrations, close to the minimum limit of audibility, has awave length of about 10 feet. At the middle of the scale of sound, about 5,000 vibrations, the wave is-still' about 2 feet long; At the upper *range of the-scale-of audibility, 20,000vibrations, the wave length is -about 2'- inches, still an appreciable amount. Aboutlsquare inch of free diaphragm area-is the irreducible minimum if'any results are-to be expected without introducing an outside power'source.

' The-intensity or power of the wave must also be considered. The minimum audible sound'for a normal-"ear, usually, taken at ten to the minus sixth power per square centimeter, cannot" be detectedevenwith themost advanced external power; amplification: This invention is not con cerned-" with this low-limit, norwith the loudest sounds, which have-power'of the order of about 50 atmosph'eres' or 700 pounds per square inch. The=sound 'range -where--my acoustic device is of chief value is from to decibels,wherethe power-is. of the order of about'i atmosphere, or

1 pound persquare -inch'. For a sound of 5,000

vibrations andpower 05'1- pound per square inch the diaphragm 'must moveatthe rate of 5,000

complete cycles per second with the 'exertion'of cannot be 'm'ade -so small as 'to' beinconspicuous.

With a device. of the I proportions illustrated in thel-drawings and having as I a minimum one-- square inch of diaphragm area within the circular slit the relation of the diaphragm to sound waves of moderate loudness and to its casing will be such that its vibration within the casing will have sumcient force and amplitude to prevent the passage of sound waves which might damage the ear.

The improved acoustic guard, being small and light in weight, can be worn without discomfort or inconvenience, and since it does not interfere with the wearers perception of ordinary sounds, is adapted for use in places where ear plugs of the old types cannot be worn. The materials for the guard, hard rubber or plastics of suitable characteristics for the casing, anchor and fixed center piece, neoprene or soft rubber for the re= movable tip, and cellulose acetate or similar material for the diaphragm, are strong and light, and the sensitive diaphragm is mounted so as to be protected from injury or tampering.

The ear fitting is especially advantageous because it is practically universal, as one size will fit practicaly all ears. It is much more effective as a seal for the entrance to the ear canal than fittings molded to the individual ear, and much more practical and less expensive. The flextible, articulating neoprene tip mounted on the rigid stem provides an automatic accommodation to the varied angles and irregularities of the entrance to the ear canal, since the tip can be deflected to the fill the entrance completely and gives a firm, yielding contact at all points.

While I have illustrated and described the preferred embodiments of my invention, it is to be understood that I do not limit myself to the precise constructions herein disclosed and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In an acoustic device, a circular sound muffling casing having openings in opposite faces and seats surrounding the interior edges of said openings, a diaphragm having a passage therethrough out of alignment with said openings mounted in said case and adapted to restrict said openings alternately by vibration between said openings, and means on said casing for mounting said device on the ear, said means comprising an anchor and a tip having a passage therein communicating with the opening in adjacent side of the casing, said tip being adapted to engage the entrance to the ear canal and said anchor being adjustably disposed with reference to the tip and adapted to engage an opposed portion of the ear.

2. In an acoustic device, a flattened sound muffling casing having openings in opposite faces and having fiat seats around the inner margins of said openings, and a diaphragm mounted in the center of said casing and extending across the casing from side to side between said casing openings, said'diaphragm having a free central portion hinged to its margin by an integral bridge, said diaphragm being sufliciently non-responsive to permit the passage of sounds of ordinary intensity but vibrating to restrict the openings alternately when subjected to loud noises to reduce the intensity of the sound transmitted to the ear.

3. In an acoustic device, a flattened sound muting casing having openings in opposite faces and having fiat seats around the inner margins of said openings, and a diaphragm mounted in the center of said casing and extending across the casing from side to side between said casing openings, said diaphragm comprising a circular sheet having an aperture near the margin and a slit extending around the margin at the same distance from the center as the aperture and terminating adjacent the aperture at both ends, forming a free central portion of the diaphragm hinged to the margin by an integral bridge, said diaphragm being sufiiciently non-responsive to permit the passage of sounds of ordinary intensity through the slit and aperture but vibrating to restrict the openings alternately when sub jected to loud noises to reduce the intensity of the sound transmitted to the ear.

4. An acoustic device comprising a casing provided with sound mufflng means and means for mounting it on the ear, said second-mentioned means comprising a tip mounted on said casing at an acute angle thereto and having a sound passage therethrough communicating with the casing and the entrance to the ear canal, and an anchor on said casing extending in opposed relation to the tip, said tip and anchor being relatively adjustable for engagement with ears of different shapes and sizes.

5. An acoustic device comprising a casing provided with sound muffling means and means for mounting it on the ear, said second-mentioned means comprising a tip mounted on said casing and having a sound passage therethrough communicating with the casing and the entrance to the ear canal, and an anchor on said casing extending in opposed relation to the tip, said anchor being movably mounted on said casing and biased in a direction away from said tip.

6. An acoustic device comprising a sound muffiing casing and means for mounting it on the ear, said means comprising a tip mounted on said casing and having a sound passage therethrough communicating with the casing and the entrance to the ear canal, an anchor extending in opposed relation to said tip, and means for mounting said anchor on said casing, said means comprising a slide to which said anchor is secured, a trackway for said slide on said casing and means for urging said slide toward the end of said trackway to move said anchor away from said tip.

'7. An acoustic device comprising a sound muffling casing and means for mounting it on the ear, said means comprising a tip mounted on said casing and having a sound passage therethrough communicating with the casing and the entrance to the ear canal, and an anchor on said casing extending in opposed relation to the tip, said tip comprising tw telescopically connected sections, the ear-engaging section being removably mounted on the section attached to the casing, and having a series of segments at its telescoping end, said segments being separated by constricted portions adapted for engagement by cutting means to shorten the length of the tip to fit the ear of the wearer 8. Supporting means for an acoustic device comprising a tip mounted on said device adapted to engage the entrance to the ear canal and an anchor on said device extending in opposed relation to the tip, said anchor being movably mounted on said device and biased in a direction away from said tip.

9. Supporting means for an acoustic device comprising a tip mounted on said device and adapted to engage the entrance to the ear canal, an anchor extending in opposed relation to the tip, and means for mounting said anchor on said device, said means comprising a slide to which said anchor is secured, a trackway on said device for'said slide and means for urging said slide toward the end of'said trackwayremote'from said tip.

10; A mechanical vibrator for-reducing the-intensity of sound comprising a casing. and means for supporting it in theear, said casing and supportin'gmeans having *a passage for sound and shutting off external sound from the ear, and a diaphragm within the casing, said casing being flattened and-provided with opposed openings forming. part of the sound passage and said diaphragm lying flatwise and'vibrating between said openings, said diaphragm having a minimum area'of one square inch.

11. Supporting means for an acoustic device comprising a tip mounted on said device adapted to engage the entrance to the ear canal andan anchor on said device extending in opposed relationto the tip, said tip comprising telescopically connected sections, and one of said sections having a series of annular segments separated'by constricted portions adapted for engagement by cutting means to shorten the length of the tip to fit the ear of the wearer.

12'. In an acoustic device, a sound mufiling casing having inlet and outlet openings and'havinginterior seats around said openings, anda diaphragm mounted in said casing and extending across the casing between said openings, said 8 diaphragmEhaVing a substantially free central portion hinged-to its margin, and said diaphragm bein sufliciently nonresponsive to permit the passage of sounds f ordinary intensity but vibratingeto restrict the openings alternately when subjected to loud-noises to reduce the intensity of the sound transmitted to the ear.

MAURICE C. ROSENBLATT.

REFERENCES CITED The-following references are of record-in the file'of this patent:

UNITED STATES PATENTS Number Name Date 1,279,396 Mich'elsen et al. Sept. 17, 1918 1,832,422 Filling Nov, 17, 1931 1,893,143 Koch Jan; 3, 1933 2,312,534 Fiene -Ma1; 2, 1943 2,361,963 Rosenlolatt Nov. 7, 1944 2,377,739 Wyckofi June 5, 1945 2,430,229 Kelsey Nov. l; 1947 FOREIGN PATENTS Number Country Date 29,050 Denmark 1 Dec.- 10, 1921 239,473 Great Britain Ma 6, 1926 365,962 Great Britain Jan. 28, 1932 428,733 Great Britain May 17, 1935 

